Electric circuit breaker with hydraulic actuating means including a plurality of valves for opening the breaker,and a plurality of valves for closing the breaker

ABSTRACT

AN ELECTRIC CIRCUIT BREAKER IS DISCLOSED HAVING A BLAST PISTON FOR COMPRESSING A GASEOUS QUENCHING MEDIUM SUCH AS SULFUR HEXAFLOURIDE, AND A HYDRAULIC DRIVE FOR THE BREAKER WHICH INCLUDES A MAIN HYDRAULIC ACTUATOR CYLINDER AND PISTON AND VALVES FOR CONTROLLING THE ADMISSION OF HYDRAULIC FLUID INTO THE CYLINDER. IN ADDITION, FOR CLOSING THE CIRCUIT BREAKER A HYDRAULIC LATCHING ARRANGEMENT IS DISCLOSED WHICH IS ASSOCIATED WITH THE VALVE CLOSEST TO THE MAIN ACTUATOR CYLINDER IN AN APPLICATION WHERE THERE ARE MORE THAN TWO SERIES-CONNECTED VALVES FOR CLOSING THE BREAKER. FOR OPENING THE BREAKER, A HYDRAULIC LATCHING ARRANGEMENT IS DISCLOSED WHICH IS ASSOCIATED WITH A VALVE WHICH IS SEPARATED FROM THE MAIN ACTUATOR CYLINDER BY AT LEAST ONE FURTHER VALVE.   D R A W I N G

United States Patent 1191 Grieger et a1.

1451 Aug; 27115174" x 122 Filed:

[ 1 ELECTRIC CIRCUIT BREAKER WITH HYDRAULIC ACTUATING MEANS INCLUDING APLURALITY OF VALVES FOR OPENING THE BREAKER, AND A PLURALITY OF VALVESFOR CLOSING THE BREAKER 175] Inventors: Gerhard Grieger; Joaquin Bohrdt,

both of Berlin, Germany [73] Assignee: Siemens Aktiengesellschaft,Munich.

Germany May 26, 1972 211 Appl. No.: 257,151

[30] Foreign Application Priority Data June 4. 1971 Germany ..2128648[52] US. Cl. 200/82 B, 200/148 A, 251/634 [51] Int. CL. H0lh 35/38, HOlh33/34, H0lh 33/88 [58] Field of Search 200/82 AB, 82 R, 148 A,

FOREIGN PATENTS OR APPLICATIONS 4.519.250 1/1967 .lapan 200/82 1,203,6321/1960 France 200/82 R Primary Examiner-Robert K. Schaefer AssistantExaminerRobert A. Vanderhye Attorney, Agent, or Firm-Hugh A. Chapin 5 7ABSTRACT An electric circuit breaker is disclosed having a blast pistonfor compressing a gaseous quenching medium such as sulfur hexaflouride,and a hydraulic drive for the breaker which includes a main hydraulicactuator cylinder and piston and valves for controlling the admission ofhydraulic fluid into the cylinder. In addition, for closing the circuitbreaker a hydraulic latching arrangement is discosed which is associatedwith the valve closest to the main actuator cylinder in an applicationwhere there are more than two seriesconnected valves for closing thebreaker. For opening the breaker, a hydraulic latching arrangement isdisclosed which is associated with a valve which is separated from themain actuator cylinder by at least one further valve.

12 Claims, 1 Drawing Figure ELECTRIC CIRCUIT BREAKER WITH HYDRAULICACTUATING MEANS INCLUDING A PLURALITY OF VALVES FOR OPENING THE BREAKER,AND A PLURALITY OF VALVES FOR CLOSING THE BREAKER BACKGROUND OF THEINVENTION 1. Field of the Invention This invention relates to anelectric circuit breaker and more particularly, to a high-voltage powercircuit breaker wherein a hydraulic drive and a hydraulic latchingarrangement are provided for the breaker, and wherein a blast piston isprovided for compressing an arc-quenching medium (such as sulfurhexaflouride gas), in which circumstances special problems are presenteddue to the large driving forces and compression employed.

2. Description of the Prior Art As illustrated by West German Pat. No.1,225,497 an electric circuit breaker having a hydraulic drive is knownwherein the actuator cylinder of the hydraulic drive is associated witha hydraulically operated main valve and two magnetically operated servovalves. In the past, for closing the circuit breaker, one of the servovalves is opened, and a piston thereby acted upon by the hydraulic fluidthen opens the main valve. Subsequently, the main valve is kept underpressure when said servo valve closes, as through a branch line equippedwith a choke off the hydraulic line leading to the cylinder, and apressure line in parallel with the servo valve is provided. The chokepermits the main valve to be reversed by the other servo valve foropening the circuit breaker without an unnecessarily large loss of oil.In such a circuit breaker the discharge crosssection of the servo valvethrough which the piston is relieved for the operation of the valve,must be larger than the cross-section constricted by the choke throughwhich the hydraulic fluid can flow into the piston.

In known circuit breakers of the type described, due to the largeactuating forces required for the circuit breaker and the small controlforces, more servo action is sometimes needed than is attainable withtwo servo valves. In such a circumstance the known drive is not only nolonger usable but there is also a danger that the known circuit breakerwill not reliably perform its important circuit-opening operation. Thus,the servo valve for the opening of the breaker may close again after ashort open period. and the hydraulic line provided for latching thebreaker upon opening may refill the cylinder having the valve-actuatingpiston. In such a circumstance the circuit breaker may then eitherremain closed or remain in an intermediate position following a briefmovement in the opening direction.

SUMMARY OF THE INVENTION It is an object of this invention to provide areliable circuit breaker.

It is another object of this invention to provide an electric circuitbreaker with reliable latching means.

It is a further object of this invention to provide an electric circuitbreaker suitable for use for high-voltage power circuits with a blastpiston for compressing a gaseous quenching medium. Other objects of thisinvention are referred to below.

With a circuit breaker according to this invention having more than twoseries-connected valves for closthe closing is associated with the valveclosest to the main hydraulic actuator cylinder, and a hydrauliclatching arrangement for the opening is associated with a valve which isseparated from the cylinder by at least one further valve.

With a circuit breaker according to this invention, it has been foundthat the desired latching is achieved without impairment of thereliability of the circuit breaker, even where there is a large ratiobetween the actuating and control forces of the circuit breaker. Due tothe fact that the latching for the closing of the breaker is assigned tothe last valve ahead of the main actuator cylinder, only the opening ofthat valve which actually acts upon the drive supplies the hydraulicfluid used for the latching arrangement. Also, it is always possible toopen the circuit breaker without having to transmit a long command.Further, by arranging the hydraulic line for latching when opening atleast one further valve ahead of the cylinder in the series of openingvalves, the hydraulic system inherently provides priority for theopening operation. In other known circuit breakers such priority isprovided by additional means, particularly additional electrical means.

The hydraulic drive of the circuit breaker according to the inventioncan also be entrusted with a task which heretofore was accomplished byelectrical interlock devices. Thus, according to a further aspect of theinvention, the valve series provided for the opening is connected to thehydraulic line used for the latching arrangement for the closing. Inthis manner an opening command can be transmitted hydraulically only ifthe circuit breaker is actually closed.

According to another feature of this invention, the valve preceding thevalve with the latching arrangement for closing can be shut off by acheck valve,

thereby permitting the preceding valve to close without causing oillosses due to the pressure in the latching line.

According to a still further feature of this invention, in the preferredembodiment of the invention the valve provided with the closing latchingarrangement is a two-three-way valve which is associated with the largerpiston surface of'a differential piston while the smaller piston surfaceof the differential piston is continuously acted upon by hydraulicfluid. In this manner, a doubleaeting hydraulic actuator can be operatedwith a single accumulator without the necessity of special venting forrapid operation. The stroke of the two-three-way valve is preferablylarger for the opening of its inlet than for the closing of its outlet,so that unnecessary losses of hydraulic fluid are avoided.

Although the invention is described herein with reference to aparticular preferred embodiment, the scope of the claims hereof are'notintended to be limited to the details shown, since various modificationsmay be made within the range and scope of the accompanying claims.

' DESCRIPTION OF THE DRAWING The accompanying drawing is a schematicrepresentation of a preferred embodiment of a circuit breakerconstructed according to this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in the drawing, thehigh-voltage power circuit breaker 1 is operated by a hydraulic actuator2. As the high-voltage circuit breaker 1 may be designed for a ratedvoltage of l 10 kilovolts or more, and a flow of sulfur hexafluoride gas(SF,,) for quenching any electrical are formed between the electricalbreaker contacts at the moment of switching is provided by means of ablast piston coupled with the movable contact 5, a considerable andreliable driving force must be provided for the device, especially forthe opening of the breaker contacts. The hydraulic actuator 2 includesan actuator cylinder 3 with a differential piston 4 contained thereinwhich is coupled by means of an insulating linkage 6 with the movablecontact of the circuit breaker.

Hydraulic fluid such as oil for operating the circuit breaker comes froma hydraulic accumulator 10 in which the fluid is kept under a suitablepressure (for instance, 200 atmg) by means of gas in known manner.Connected to the outlet 11 of the hydraulic accumulator is a pressureline 12 which leads directly to a main valve 13 interposed before themain hydraulic actuator 2 for the circuit breaker 1. The main valve 13has a passage 16 by means of which the portion of the actuator cylinder3 associated with the smaller piston surface 18 of the differentialpiston 4 of the hydraulic actuator 2 is continuously acted upon byhydraulic fluid through a hydraulic line 19 extending from the mainvalve 13.

The larger piston surface 20 of the differential piston 4 within themain hydraulic cylinder 3 is connected through a hydraulic line 21 to achamber 23 of the main valve 13 which is adapted to be shut off by avalve head 24 from the passage 16 communicating with pressure line 12and the accumulator 10. This valve head 24 is spring-biased by a spring25 which resiliently presses the valve head 24 against a valve seat 27.To actuate the valve head 24, a stem 29 is provided which is movablyreceived within a recess 30 in the valve head 24. This stem 29 is anintegral extension of the main valves actuator piston 31. The actuatorpiston 31 is guided within a cylinder 32.

At the portion of the stem 29 extending toward the piston 31, the stemwidens and forms a cylindrical valve member 33 which serves as a sliderand cooperates with a recess 34 in the cylinder such that the hydraulicconnection between chamber 23 and outlet 36 of the main valve can beclosed off.

For the hydraulic operation of the hydraulic actuator 22, a series ofvalves (39, 47, 65) is provided for the opening process and anotherseries of valves (38, 46, 13) is provided for the closing process. thetwo valve series being to some extent of similar design. For example,the two valve series each include a servo valve 38, 39 with anassociated electro-magnct 40, 41 for electrical operation thereof. Theservo valve 38 for the closing process is connected to the pressure line12 by means ofa hydraulic line 42, and the servo valve 39 for theopening process is connected by a hydraulic line 43 to a hydraulic line44 which opens into chamber 23 of the main valve 13.

The two servo valves 38, 39 are each followed by an associated controlvalve 46, 47 which is operated hydraulically. The control valve 46 forthe closing process is connected by means of a hydraulic line 50 withthe pressure line 12, while the control valve 47 for the opening processis connected by means of a hydraulic line 51 to hydraulic line 43. Therespective actuator pistons 53, 54 of the control valves 46, 47 are eachadapted to be acted upon by hydraulic fluid through their respectiveservo valves 38, 39 through respective hydraulic connecting lines 55,56. When the servo valves 38 and 39 are closed, the actuator pistons 53,54 of the control valves 46, 47 are relieved by means of hydraulic lines100 and 101 respectively.

From the control valve 46 for the closing process a hydraulic linehaving a check valve leads to the inlet 61 of the cylinder 32 for theactuating piston 31 of the main valve 13. As shown in the accompanyingdrawing, this inlet 61 is hydraulically connected with hydraulic line 44as well as to a valve 65 which is operated by means of a piston 66.Valve 65 connects the part of the cylinder 32 of the main valveassociated with the larger area of the main valvcs actuator piston 31with an oil tank 62.

In the drawing the circuit breaker l is shown in the open position. Toclose the circuit breaker, electromagnet 40 is energized in a knownmanner, thereby opening its associated servo valve 38. Hydraulic fluidthen flows to the piston 53 of control valve 46 to open the controlvalve 46, and hydraulic fluid then flows through hydraulic line 50,check valve 60 and the inlet 61 of the main valve to actuate the piston31 of the main valve 13. The piston 31 of the main valve then moves fromright to left with reference to the position of the piston shown in theaccompanying drawing. Within the main valve 13, the length of the stem29 has a predetermined relationship to that of the recess 30 in valvehead 24 and to the distance between the valve seat 34 and the slidercylinder 33 such that outlet 36 of the main valve is closed off shortlyafter the actuator piston 31 moves from right to left. Thereafter, thevalve head 24 of the main valve 13 is lifted from the valve seat 27, andthe hydraulic fluid present at valve inlet 16 is thereby permitted toflow into a hydraulic line 21 extending to cylinder 3 of the mainhydraulic actuator 2 with the result that the circuit breaker closes.Automatic latching is assured when the valve 13 opens by means of ahydraulic line 44 which bypasses the closing control valve 46, with theresult that the closed circuit breaker remains in its closed positionwhen the closing electromagnet 40 is de-energized and its associatedvalves 38 and 46 close.

To open the circuit breaker 1, servo valve 39 is opened by anenergization of electro-magnet 41 in a known manner. With the opening ofservo valve 39 hydraulic fluid is permitted to flow through hydrauliclines 44, 43 and 56 to control valve 47, and from there throughhydraulic lines and 71 to valve 65. Through the practically simultaneousopening of control valve 47 and valve 65, inlet 61 of the main valve ishydraulically connected with the oil tank 62. Through suitabledimensioning of the outlet cross-section in relation to hydraulic line44 which serves as the feed line and in which a choke 103 can bearranged, there is rapid pressure relief of the piston 31 in the mainvalve with'the result that spring 25 together with the force of thehydraulic fluid acting on the piston closes the main valve at valve seat27. The large piston surface 20 of the differential piston 4 is thenpressure-relieved rapidly and reliably by the opening of outlet 36 intoan oil tank. Thereby, the pressure of the hydraulic fluid actingcontinuously on the small piston surface 18 of the differential piston 4brings the circuit breaker l reliably into the open position.

From the drawing and the preceding description it will be seen that thehydraulic latching for the closing operation is due to hydraulic line44, and the latching arrangement is consequently located directly at themain valve 13. On the other hand. the hydraulic latching for the openingoperation is provided by hydraulic lines 51 and 71. It is accordinglypossible with the described invention to initiate the opening operationwithout having to actuate the main valve 13 itself. As a result theclosing operation starts only when the closing command is executed withcertainty, while the opening command can be given to the drive mechanismeven when there is an existing closing command. Therefore, the openingcommand, which is important for the safety of the circuit breaker. isexecuted with priority in spite of hydraulic latching for the closingoperation. The opening command remains in the latched condition as longas overpressure exists in hydraulic lines 44, 43, 51 and 56.

It will be noted that in the described embodiment of the invention whichhas more than two seriesconnected valves 13, 38, 46 for the closing. thelatching arrangement for the closing is associated with the valve 13closest to the cylinder 3 of the hydraulic actuator 2, and that ahydraulic latching arrangement 71 is also provided for the opening. Thelatching arrangement for the opening is associated with a valve 47 whichis separated by valve 65 from the cylinder 3 of the hydraulic actuator2. It will also be noted that the valves 39 47, 65 provided for theopening are connected to the hydraulic line 44 which is used for thelatching arrangement for the closing.

We claim:

1. In an electric circuit breaker for use with hydraulic fluid and witha blast piston for compressing a gaseous quenching medium. the circuitbreaker having a main hydraulic actuator. a plurality of valves forclosing the breaker. and a plurality of valves for opening the breaker.the improvement comprising means for hydraulically latching the circuitbreaker upon its closing, which means is connected to the one of thevalves for closing the breaker which is hydraulically closest to themain hydraulic actuator;

means for hydraulically latching the circuit breaker upon its opening.which means is connected to one of the valves for opening the breakerwhich is hydraulically separated from the main hydraulic actuator by atleast an additional one of the valves for opening the breaker;

an oil tank; and

a main valve having a hydraulic connection to said oil tank and ahydraulic connection to the hydraulic actuator.

2. An electric circuit breaker as in claim 1 wherein the valves foropening are hydraulically connected in series and wherein the valves forclosing are hydraulically connected in series.

3. An electric circuit breaker as in claim 1 wherein the means forlatching the circuit breaker upon its closing includes a hydraulic linebetween the main valve and said one of the valves for closing.

4. An electric circuit breaker as in claim 3 wherein the means forlatching the circuit breaker upon its opening is connected to saidhydraulic line.

5. An electric circuit breaker as in claim 3 wherein said hydraulic linehas a check valve therein for shutting off said one of the valves forclosing.

6. An electric circuit breaker as in claim 1 wherein S the main valve isa two-three-way valve, and

i the hydraulic actuator includes a differential piston with its largerpiston surface having a hydraulic connection to said two-three-wayvalve, and'its smaller piston surface being continuously acted upon byhydraulic fluid.

7. An electric circuit breaker as in claim 6 further comprising the oiltank being hydraulically connected to an outlet of said two-three-wayvalve and wherein the stroke of said two-three-way valve for opening itssaid hydraulic connection to said differential piston is larger than thestroke of said two-three-way valve for closing its said outlet to saidoil tank.

8. An electric circuit breaker as in claim 1 wherein two of the valvesfor opening the breaker are respectively identical to two of the valvesfor closing the I breaker.

9. In an electric circuit breaker for use with hydraulic fluid and witha blast piston for compressing a gaseous quenching medium, the circuitbreaker having a main hydraulic actuator, a plurality of valves forclosing the breaker, and a plurality of valves for opening the breaker.the improvement comprising means for hydraulically latching the breakerupon its closing, which means is connected to the one of the valves forclosing the breaker which is hydraulically closest to the main hydraulicactuator;

means for hydraulically latching the circuit breaker upon its opening.which means is connected to one of the valves for opening the breakerwhich is hydraulically separated from the main hydraulic actuator by atleast an additional one of the valves for opening the breaker;

an oil tank; and

a main valve having a hydraulic connection to said oil tank and ahydraulic connection to the hydraulic actuator,

which hydraulic actuator includes a differential piston with its largerpiston surface having a hydraulic connection to the main valve and itssmaller piston surface being continuously acted upon by the hydraulicfluid. and

which main valve comprises a two-three-way valve in which the stroke ofthe piston for opening its said hydraulic connection to the differentialpiston is larger than the stroke of the piston for closing its saidhydraulic connection to said oil tank.

10. An electric circuit breaker as in claim 9 wherein said two-three-wayvalve comprises a spring-biased valve head with a recess therein, saidvalve head being within a chamber in said twothree-way valve; and

a piston within said two-three-way valve. said piston having a stemportion adapted to be received into the recess in said valve head formoving said valve head in a direction opposite to the spring-bias ofsaid valve head.

11. An electric circuit breaker as in claim 9 which further comprises amoveable contact for opening and closing the circuit in which thebreaker is interposed; and

means for linking said piston of said differential piston to saidmoveable contact. 12. An electric circuit breaker as in claim 9 whereinthe valves for closing the breaker and the valves for opening thebreaker each include an electromagnetically actuated servo valve.

